<template>
  <div class="pagination">
    <button :disabled="pageNo==1" @click="$emit('getPageNo', pageNo-1)" >上一页</button>
    <button v-if="startNumAndEndNum.start>1" @click="$emit('getPageNo', 1)" :class="{active: pageNo == 1}">1</button>
    <button  v-if="startNumAndEndNum.start>2">···</button>
    <template v-for="(page,index) in startNumAndEndNum.end">
        <button :key="index" v-if="page>=startNumAndEndNum.start" @click="$emit('getPageNo', page)" :class="{active: pageNo == page}">{{page}}</button>
    </template>
    <button v-if="startNumAndEndNum.end<totalPage-1">···</button>
    <button v-if="startNumAndEndNum.end<totalPage" @click="$emit('getPageNo', totalPage)" :class="{active: pageNo == totalPage  }">{{totalPage}}</button>
    <button :disabled="pageNo==totalPage" @click="$emit('getPageNo', pageNo+1)">下一页</button>
    
    <button style="margin-left: 30px">共 {{total}} 条</button>
  </div>
</template>

<script>
  export default {
    name: "Pagination",
    props:['pageNo', 'pageSize', 'total', 'continues'],
    computed:{
        // 计算总共多少页
        totalPage(){
            return Math.ceil(this.total/this.pageSize)
        },
        // 计算出连续的页码的起始数字和结束数字
        startNumAndEndNum(){
            let start = 0, end = 0
            // 连续页码数字5【就是至少是5】
            if(this.continues>this.totalPage){
                start = 1
                end = this.totalPage
            }else{
                start = this.pageNo - Math.floor(this.continues/2)
                end = this.pageNo + Math.floor(this.continues/2)
                if(start < 1){
                    start = 1
                    end = this.continues
                }
                if(end > this.totalPage){
                    end = this.totalPage
                    start = this.totalPage - this.continues + 1
                }
            }
            return {start,end}

        }
    }
  }
</script>

<style lang="less" scoped>
  .pagination {
      text-align: center;
    button {
      margin: 0 5px;
      background-color: #f4f4f5;
      color: #606266;
      outline: none;
      border-radius: 2px;
      padding: 0 4px;
      vertical-align: top;
      display: inline-block;
      font-size: 13px;
      min-width: 35.5px;
      height: 28px;
      line-height: 28px;
      cursor: pointer;
      box-sizing: border-box;
      text-align: center;
      border: 0;

      &[disabled] {
        color: #c0c4cc;
        cursor: not-allowed;
      }

      &.active {
        cursor: not-allowed;
        background-color: #409eff;
        color: #fff;
      }
    }
  }
  .active{
      background-color: skyblue;
  }
</style>